Globular clusters are bound collections of stars in the halo of a galaxy. There are approximately 150 globular clusters in our Galaxy. Globular clusters are often searched for pulsars as 1) they contain a high fraction of millisecond pulsars and 2) their angular size is small allowing for a single, long observation. As globular clusters have a very high star density, close interactions are common. It is thought that the millisecond pulsars arise from such interactions.

Turk & Lorimer (2013) described a Bayesian method that can be applied to studying the pulsar population in a globular cluster. The number of pulsars in any given cluster depends upon the parameters of the globular cluster. In particular Hui et al. (2010) proposed a relationship between the pulsar abundance in a particular cluster and the stellar encounter rate, Γ{\displaystyle \Gamma }.

The best fit model from the Turk & Lorimer (2013) paper suggested that the number of pulsars in a specific globular cluster, Npsr{\displaystyle N_{\rm {psr}}} is

where μ=−1.1{\displaystyle \mu =-1.1} and σ=0.9{\displaystyle \sigma =0.9} are reasonable values and Lmin{\displaystyle L_{\rm {min}}} is the extrapolated luminosity sensitivity at an observing frequency of 1400 MHz (note that Lmin=SminD2{\displaystyle L_{\rm {min}}=S_{\rm {min}}D^{2}} where D{\displaystyle D} is the distance to the globular cluster).

McLaughlin et al. (2003) carried out a large-scale search for giant pulses coming from extragalactic pulsars, but did not make any convincing detections. As described below Rubio-Herrera et al. (2013) used Westerbork to search for pulsars in M31. Kondratiev et al. (2013) used the Green Bank and Arecibo telescopes to search for pulsars in nearby galaxies.

Rubio-Herrera et al. (2013) used the Westerbork Synthesis Radio Telescope (WSRT) to search for radio pulsars and fast transients in M31. This search did not find any periodic sources, but they tentatively found some burst events with a dispersion measure of 55cm-3pc which, they argued, placed these objects outside of our Galaxy. These burst signals have not been redetected.